Preparation of hydroxyl terminated polymers

ABSTRACT

Hydroxyl terminated polymers, useful as adhesives and caulking materials, are prepared by the reaction of carboxyl terminated polymers with a diol in the presence of an acid catalyst.

United States Patent Siebert 51 Oct. 17, 1972 [54] PREPARATION OFHYDROXYL TERMINATED POLYMERS [56] References Cited {72] Inventor: AlanR. Siebert, Maple Heights, OTHER PUBLICATIONS Ohio Royals, E. G.Advanced Organic Chemistry pp. 600- [73] Assrgnee: The B. F. GoodrichCompany, New Y 601 York, N.Y. 22 F1 d: l 1 Primary Examiner-Lorraine A.Weinberger 1 l e y 2 970 Assistant Examineh-Paul J. Killos PP 52,075Attorney-Albert C. Doxsey and J. Hughes Powell, Jr. Related u.s.Application Data 57] ABSTRACT I [62] PDivisIiIon of Ser. No. 731,269,May 22, 1968 Hydroxyl terminated polymers, useful as adhesives andcaulking materials, are prepared by the reaction f b It 'tdl 'th dl"th52 use]. ..260/484 R, 260/486R g gjg fif ,;;1;,,;{ a m 511 Im. Cl...C07c 6 9/66 [58] Field of Search ..260/484 AR, 486 R 4 Claims, NoDrawings l PREPARATION OF HYDROXYL TERMINATED POLYMERS CROSS REFERENCETO RELATED APPLICATION This application is a division of copend'ingapplication Ser. No. 731,269 now U.S. Pat. No. 3,551,472 filedMay 22,1968 by A. R. Siebert.

- BACKGROUND OF THE INVENTION Hydroxyl terminated liquid olefinicpolymers are useful as crosslinking agents with difunctional polymers,as adhesives, and as caulking and potting compounds. They 'cure readilythrough reaction of the terminal hydroxyl groups with organicdiisocyanates to form solid high molecular weight materials of lowfusibility.

run at 70 80 C. Product polymer is thrown down These liquid polymers maybe hydroxyl terminated homopolymers such as polybutadiene and highlysaturated polymers such as polyalkyl acrylates whose alkyl moitiesconsist of one eight carbon atoms.

Hydroxyl functional polymers can be produced from olefinic polymers byfirst converting a portion of the olefinic bonds of the polymer toozonide linkages, and then reductively cleaving the ozonide linkages toproduce hydroxy terminated polymer.

Alternative processes of manufacture are desirable and constantly beingsought in the art. Furthermore, polymers prepared by cleavage of highermolecular weight chains as described above generally do not achievehydroxyl functionality at each end of the polymer chains, tha is, thefinal hydroxyl functionality is generally considerably less than 2,often- L6 to 1.8. For most efficient use of the reactants and theobtainment of the best overall properties, it is desirable to have finalhydroxyl functionality as close to 2.0as possible.

SUMMARY OF THE INVENTION Carboxyl terminated polymers of polybutadieneand polyalkyl acrylates are known in the art. It has now been discoveredthat it is possible tojreadily convert these carboxyl terminated liquidpolymers to hydroxyl terminated liquid polymers with a high degree ofdifunctionality, i.e., practically 2, indicative of the fact that anhydroxyl group is located at each end of the polymer chain. The propertyof difunctionality is essential if higher polymers are to be produced bythe subsequent curing reactions. This conversion is accomplished byreaction of a liquid carboxyl terminated polymer with a 10 fold excessof a difunctional hydroxy compound, preferably a liquid diol of theformula HO--ROl-l where R is a methylene chain of three to six carbonatoms in the presence of 0.3 to 0.5 parts of an acid catalyst. Water ofreaction forms as a by-product and must be removed either by having itdissolve in the reaction medium or'by distilling it off,

preferably at atmospheric pressure, below the boiling point of thereaction medium. Reaction media then are solvents that will dissolve thecarboxyl terminated polymers,and the hydroxyl terminated polymers whichare formed and will either (1) dissolve up to 5 percent of their ownweight of water, or (2) have a boiling point greater than 110 C. so thatwater of reaction canbe distilled off at l00 C. without loss of solvent.Acetone,

cyclohexanone are typical solvents.

with methanol and separated by decantation. These carboxyl terminatedpolymers are curable with diisocyanates. It has been discovered thatwhen liquid carboxyl terminated polymer is reacted with a difunctionalhydroxyl compound, preferably a diol, in the presence of. an acidcatalyst, the chain terminal group is opened up and converted fromcarboxyl to hydroxyl. The preferred diol is l,4 -butanediol. Catalyststhat may be employed in the range of 0.3 to 0.5 parts per hundred ofpolymer include mineral acids such as hydrochloric, sulfuric andphosphoric acids and organic acids such as p-toluene sulfonic acid andthe like. The preferred catalyst is dodecyl benzene sulfonic acid.

Molecular weights of the polymers are determined with a Mechrolab VaporPressure Osmometer using methylethyl ketone (MEK) or toluene as thesolvent. I

The instrument is calibrated with azobenzene and sucrose octaacetate.Molecular weight may also be calculated from the chemicalequivalents perhundred of rubber of carboxyl.(ephr) value determined by titration ofpolymer solution with alcoholic KOH to a phenolphthalein endpoint.Functionality of the polymer is defined as the ratio of the osmometermolecular weight (corrected for antioxidant, if any is present) to thecalculated ephr molecular weight times 2, the ideal number of carboxygroups per molecule.

Brookfield viscosity employing an LVT model viscometer and a No. 4spindle is run on freshly prepared polymers at 27 C. Values up to 50,000

80,000 cps. are accepted by the art as indicative of pourable, easilyhandled materials.

DETAILED DESCRIPTION OF THE lNVENTlON EXAMPLE 1 TABLE 1 Tertiary butanolpans 100 Butadiene l 00 Azodicyanovaleric acid 4 Temperature "C.Polymerization time 16 hrs. Polymer yield 14.8 g. COOH/Ephr (equivalentper hundred parts rubber) .0598 Brookfield viscosity at 27C. 26,500 cps.Mn-MEK 3380 Mn-calc. 3340 Functionality 2.02

100 parts of carboxyl terminated polymer are added with 100 partssolvent to a 3 neck flask equipped with thermometer and agitator. Excessbutanediol-l,4 is added calculated on the basis of one mol-butan ediolper mol of --COOH. Sulfonic acid is employed as a catalyst, the flask isheated to drive the reaction. Water of reaction dissolves in the acetonesolvent in (A) and forms a distillable azeotrope in (B). Run (A), inacetone, is conducted in a sealed system to run the reaction at 96 C.Run B, in toluene, is conducted at 1 16 C. to drive the reaction andremove the solventwater azeotrope. Reaction is followed by titrating analiquot from the bottle with standard base using phenolphthaleinindicator. The hydroxy] terminated polymer is recovered by addingmethanol to throw down the polymer. Potassium hydroxide is added toneutralize the excess acid catalyst. The polymer layer is decanted anddried on a Rinco evaporator.

Data observed on the hydroxyl terminated polybutadiene is listed inTable 2 below:

TABLE 2A B Carboxyl terminated Brookfield viscosity at 27C. Pot lifewith [.0 equivalent of toluene diisocyanate 27,000 cps 22,000 cps Theproducts serve as excellent caulking compounds, being soft and workableinitially and setting up gradually to a dry, but yielding state.

When the example is repeated using in place of carboxyl terminatedpolybutadiene, a carboxylic poly-N- but yl acrylate having 0.102equivalents of COOH/EPHR, the products similarly show an almost completedisappearance of. COOH groups and when combined with 1.0 equivalent oftoluene diisocyanate they have a pot life of greater than 2 hours andshow favorable adhesive properties.

What is claimed is: v

1. Liquid hydroxyl terminated polymers selected from the groupconsisting of polybutadiene or polyalkyl acrylates whose alkyl moietyconsists of one to eight carbon atoms prepared by the reaction of liquidcarboxyl terminated polymers of polybutadiene or polyalkyl acrylateswhose alkyl moiety consists of one to eight carbon atoms, said carboxylterminated polymers being prepared bythe reaction of butadiene monomerormonoalkyl acrylates in tertiary butanol at C. in the presence of abis-azocyano acid initiator with a molar excess of a liquid difunctionalhydroxy compound of the formula HO-R-OH wherein R is a methylene chainof three to six carbon atoms in the presence of 0.3 to 0.5 part perhundred of polymer an acid catalyst selected from the group consistingof hydrochloric, sulfuric, phosphoric, p-toluene sulfonic and dodec lbenzene sulfonic acids in a reaction medium COl'lSlS mg of a solventcharacterized by power to dissolve up to 5 percent of its own weight ofwater or having a boiling point greater than C, said reaction mediumbeing maintained at 96 1 16 C.

2. The liquid hydroxy] terminated polymers of claim

2. The liquid hydroxyl terminated polymers of claim 1 where the amountof said hydroxy compound is 5 - 30 parts per hundred parts of liquidcarboxyl terminated polymer and is calculated to be a 5 - 10 fold excesson the basis of one mole of said hydroxy compound per mole of -COOH. 3.The liquid hydroxyl terminated polymers of claim 1 where the liquidcarboxyl terminated polymer is polybutadiene.
 4. The liquid hydroxylterminated polymers of claim 1 where the liquid carboxyl terminatedpolymer is polybutyl acrylate.